EP 1 348 932 A2 describes a method and a device with which a beam of light is passed through the bottle in a direction perpendicular to the axis of the bottle to thereby ascertain the wall thickness based on the measured absorption of radiation. This may be done at various heights along the bottle.
DE 101 16 665 A1 describes a method for controlling a blow-molding operation in which the wall thickness of a container is detected immediately after it is produced and then is compared with an ideal wall thickness so the manufacturing process is subsequently adapted to obtain the smallest possible differences between the actual wall thickness and the ideal wall thickness.
With this method and device, it has been found that definitive bottles cannot always be detected reliably.